(1) Field of the Invention
The present invention relates generally to acoustic towed arrays, and more particularly to a magnetic heading sensor alignment and roll reducing device for accurately positioning a magnetic heading sensor in a towed line array and for reducing unwanted roll movement of the sensor when the towed array is deployed and operated.
(2) Description of the Prior Art
Towed line arrays are used extensively in submarines, surface ships and oil exploration for detection purposes. A towed acoustic line array includes a liquid-filled hose containing a linear array of hydrophones for sound detection and magnetic heading sensors for position determination. A mechanically rugged KEVLAR sheet or web is wrapped around the various elements, which is then placed inside a liquid filled hose.
The hydrophones and magnetic heading sensors are distributed inside the hose in a predetermined configuration together with their associated electronics including their power sources. These sensors are generally different types depending upon operational requirements. The towed line arrays form an acoustic beam pattern which is used for the detection of targets in the area under surveillance. Additionally, it is important to accurately determine the position of the acoustic sensors and the towed line array as a function of time. Towards this end, a series of magnetic heading sensors are distributed along the length of the towed line array. It is desirable to have relatively small magnetic heading sensors for accurate position determination.
It is imperative to keep the magnetic heading sensors aligned within the hose and symmetrical with respect to the longitudinal axis passing through the center of the hose. Any misalignment of the magnetic heading sensors results in erroneous heading measurements. In an effort to solve this problem, U.S. Pat. No. 5,034,712 discloses a magnetic heading sensor alignment device for maintaining a sensor along the longitudinal axis of a surrounding hose. However, the sensor is still subject to pitch, yaw and/or roll in accordance with movement of the towed line array as it is deployed and operated. Although operationally unavoidable, such movement causes the sensor to react unfavorably leading to electromagnetically induced error (i.e., by movement of conductors through a magnetic field). It is therefore desirable to have a simple device which will not only maintain the sensor position along the central longitudinal axis of the hose, but also reduce as much ambient unwanted movement of the sensor as possible.